1. Technical Field
The present invention is related generally to roller hearth or other heat treating furnaces. More particularly, the present invention is related to an inspection system for such furnaces. Specifically, the present invention is related to the use of a camera for inspecting the interior of such furnaces.
2. Background Information
Roller hearth furnaces are well known in the art and typically include a heating section and a cooling section for heating and cooling various workloads as they move along a generally horizontal elongated path through the interior chamber of the furnace. By way of example, U.S. Pat. Nos. 2,175,233 granted to Vaughan, 2,634,083 granted to Baker, 3,806,312 and 3,947,242 granted to McMaster et al, 4,330,268 granted to Kremheller et al, 4,527,974 granted to Carraroli et al, and 4,932,864 granted to Myiabe, all disclose roller hearth furnaces, the contents of said patents being incorporated herein by reference.
Roller hearth furnaces may be used at relatively low heating ranges, for example, 200 to 400 or 500 degrees F., for the purpose of baking bread or any other workloads which would be heated to such a temperature range. Higher temperature roller hearth furnaces are also well known in the art for heating metals, glass, ceramic materials and the like. For example, such furnaces may be used for annealing steel or other metals. In the case of annealing steel, the steel objects are typically heated to slightly above hardening temperature, somewhere on the order of 1700 degrees F. (925 degrees C.) and cooled quickly to a temperature at which transformation should take place, which is typically on the order of about 1200 degrees F. (650 degrees C.), held at this temperature until transformation has taken place and then cooled. Copper brazing furnaces may also be used to produce copper brazed assemblies or parts or sintered parts formed from powdered metals. Such parts may be, for example, heated up to 2100 degrees F. (1150 degrees C.) depending upon the specific materials used in forming the workload. Another example is the heating of sheets of glass or metal. The previous listing is by way of example only since roller hearth furnaces can be used for heat treating any material desired. Roller hearth furnaces typically have a relatively small vertical clearance above the internal conveyor rolls which are externally driven to carry various types of workloads through the furnace for heating and cooling thereof. For this reason and others, the inspection of the interior of the furnace may be substantially impossible by direct observation without taking various portions of the furnace apart, such as opening up a given furnace section in order to inspect its interior.
There is a variety of other heat treating furnaces which are generally horizontally elongated for heating workloads as they move from an entry end to an exit end thereof. Each of these types of furnaces utilizes a conveyor system for conveying a workload to be heated therethrough. For instance, a pusher furnace utilizes a pusher assembly which may have one extendable-retractable pusher or two of such pushers which operate in an alternating fashion in order to push pusher plates with workloads thereon along one or more slide rails extending through the furnace chamber such that the pusher assembly is pushing a series of pusher plates which are sequentially in contact with one another along the length of the furnace chamber. Other conveyor systems may include one or more conveyor belts, chain conveyers, walking floors and so forth. While some of these furnaces may have an interior chamber of suitable dimensions to allow a person to move through the chamber to directly observe and inspect the chamber walls, heaters, cooling devices and so forth, there maybe other reasons why a person should not enter the furnace chamber.
It is generally preferred not to shut down or not to completely shut down such furnace systems, not only to minimize production down time and energy costs, but also to minimize the negative effects of thermal contraction and expansion when the furnace is cooled for inspection and then reheated for operational purposes. Thus, it would be preferable to inspect the furnace chamber without reducing the heated chamber any more than necessary. Even maintaining the furnace at relatively lower temperature ranges such as 150 to 200 degrees F. would typically make it prohibitive for an individual to personally enter the furnace chamber in order to perform an inspection. There is thus a need in the art for an inspection system for such furnaces which eliminates the need for an individual to enter the furnace chamber even if the physical dimensions are sufficient for that purpose, to eliminate the need for disassembling portions of the furnace in order to inspect the interior chamber, and to minimize the reduction of the temperature of the furnace in order to perform such an inspection.